【作者】 张利娟；

【导师】 郭家钢；

【作者基本信息】 中国疾病预防控制中心 ， 流行病与卫生统计学， 2008， 硕士

【摘要】 我国现有钉螺面积34.2亿m~2,其中江湖洲滩地区的有螺面积占94%以上。这类地区具有“春湿、夏淹、秋露、冬干”的特征,每年洪水上涨时,形成一片汪洋,秋季水退之后,洲滩暴露,植被丰茂,一般每年水淹3-5个月,地面长期保持潮湿,特别是芦苇杂草丛生的洲滩,非常适合钉螺孳生。钉螺的孳生对水有严格的要求,幼螺发育期间离不开水,成螺长期淹于水中则存活率下降,而且水的分布对钉螺生存必需的植被也有很大影响,干旱之处湖草难以丛生,而长期被水淹的地方湖草也可被毁,所以了解洲滩地区水位及水淹变化对于掌握钉螺的分布具有重要意义。随着遥感技术的发展,其在提取湖泊水域范围方面的应用也越来越多,而湖泊水域面积变化很大程度上受水位变化影响,因而在了解水位变化对螺情变化影响的基础上,可运用遥感技术预测洲滩钉螺的分布状况。第一部分试点区的血吸虫病流行状况马家湾及门前滩洲位于星子县蓼南乡渚溪村。该试点区05、06及07年活螺密度分别为4.74、0.85及3.37只/0.1m~2,感染螺密度05年为0.0018只/0.1m~2,06及07年未压出阳性螺,人群感染率分别为3.35%、1.59%及2.31%,耕牛感染率分别为12.31%、3.23%及3.03%。第二部分运用遥感技术分析鄱阳湖区水面面积变化本研究收集1998-2006年间的12景遥感影像,对其进行几何校正,提取MNDWI值,并设定阈值,建立掩膜,然后划定感兴趣区求取鄱阳湖的水面面积。对遥感影像中提取的鄱阳湖区的水域面积与星子、湖口及康山当日的水位进行相关性分析,相关性均较强,相关系数分别为0.957、0.893及0.939,然后以鄱阳湖区水域面积与对应的星子站当日水位建立模型,其中对数模型的拟合效果较好,R=0.959,R~2=0.920,校正R~2=0.912,模型为S=5181.5111n(h)-10261.9,其中S:鄱阳湖区水域面积,h:获取卫片当日星子水文站水位。利用2006年11月6日的TM遥感影像对鄱阳湖主体水域-水位模型进行验证。结果表明,采用模型计算出的水域面积与遥感图像测算的结果相差较小,运用影像提取的水域面积为1658.73km~2,用模型估算的水域面积为1648.20km~2,相差较小,误差小于0.64%。说明运用遥感技术提取的水域面积可以较好地反映鄱阳湖区水位变化趋势,从而为将遥感技术应用于洲滩钉螺分布的预测提供了保证。第三部分小范围研究水位变化对螺情的影响在血吸虫病的传播链中,水是必不可少的载体,且水与钉螺的孳生繁殖是密不可分的,水位的变化对于钉螺分布具有重要影响,有必要对水位变化对螺情的影响展开研究。本研究先从小范围上分析了水位变化对螺情状况的影响,收集星子水文站1997-2007年的水位资料,以分析水位变化对渚溪试点区及星子县钉螺分布状况的影响。经相关统计分析发现渚溪试点区活螺框出现率与星子站上一年度8月份月平均水位间呈负相关,相关系数r=-0.748,p=0.013＜0.05,此外渚溪试点区活螺框出现率还与上一年度丰水期平均水位及年最高水位间呈负相关,结果分别为r=-0.652,p=0.041＜0.05及r=-0.771,p=0.009＜0.01。由此可推测丰水期水位越高,淹水时间越长,钉螺死亡率越高,活螺框出现率越低。此外,星子县湖沼型钉螺面积与星子站4月份月平均水位之间呈负相关,结果为:r=-0.761,p=0.011＜0.05,说明洲滩初涨水期间提前涨水或水位升高,有螺面积减少。第四部分大范围上研究水位变化对有螺面积的影响为了进一步验证第二部分的结果,以星子站月平均水位代表鄱阳湖水位与江西省湖沼型钉螺面积之间进行相关性分析。结果发现江西省湖沼型钉螺面积与鄱阳湖4月份月平均水位呈负相关,r=-0.658,p=0.039＜0.05,进一步说明四月份涨水越晚水位越低则钉螺面积越大。本研究第二部分对遥感影像提取的水域面积与实际的水位信息之间进行了论证,而第三四部分的结果表明查螺前一年8月份的月平均水位及查螺当年4月份的月平均水位高低影响着钉螺的分布及有螺面积,因此在实际应用中可收集4月份及8月份的卫片通过提取水域面积来预测钉螺分布及钉螺面积。更多还原

【Abstract】 The total area of Oncomelania snail habitats in China is now 3.42billion m~2,and among which more than 94 percent is located in marshland and lake regions.These regions are wet in spring,submerged in summer,exposed in fall and dry in winter. Every year when flood rises,the bottomlands change into a vast ocean,and after water secedes in fall,the bottomland is exposed and vegetation is flourishing.In general,marshland submerged for 3-5 months and keeps wet for a long time, especially bottomland covered with reeds,is fit for snail surviving.The snail habitat is strictly limited with water.Young snails cannot live without water during growth,and the survival rate of adult snails will decline if the snails submerged in water for a long time.And the distribution of water can also influence vegetation,which is necessary for the survival of snails;grass cannot cover dry land or bottomland submerged in water for a long time.Therefore,it is important to find out the impact of water level on the distribution of snails at bottomland regions.With the development of remote sensing techniques,it has been more and more applied in distilling water extents of lakes,and the areas of water is influenced by changes of water level to a large extent.Thus on the basis of understanding the impact of water level on the situation of snails,we can apply remote sensing technology to forecast the distribution of snails at bottomland.Part 1:The epidemic situation of schistosomiasis in experimental areaMajiawan and Menqian marshland is located in Zhuxi village,Liaonan township, Xingzi County.The density of live snails was 4.74,0.85 and 3.37/0.1m~2 in 2005, 2006 and 2007,respectively.The density of infected snails was 0.0 018/0.1m~2 in 2005, and no infected snails were checked out in 2006 and 2007.The infection rate of population was 3.35%,1.59%and 2.31%respectively in the three years,and the infection rate of cattle was 12.31%,3.23%and 3.03%,respectively.Part 2:Analyzing the change of areas of water surface of the Poyang Lake by applying remote sensing techniqueWe collected 12 TM images between 1998 and 2006,performed geometric correction,extracted MNDWI value,set threshold value,built mask and then chose regions of interest(ROI) to calculate the areas of the Poyang Lake.We did correlation analysis between water areas of the Poyang Lake and water level of Xingzi,Hukou and Kangshan,and the correlation is strong,the coefficient of correlation is 0.957, 0.893 and 0.939,respectively.We built a model to describe the relationship of water areas of the Poyang Lake and water level of Xingzi,and the logarithm model is better, R=0.959,R~2=0.920,and adjusted R~2=0.912.The model is S=5 181.51lln(h)-10 261.9, S stands for the water areas of the Poyang Lake extracted by TM images,h stands for water level of Xingzi.We checked the model by water areas of the Poyang Lake extracted from TM image of December 6th,2006,and the result showed that the difference between water areas extracted from TM images and water areas calculated by the model is small.The former is 1 658.73km~2,and the latter is 1 648.20km~2,and the error is less than 0.64 percent.These suggested that water areas extracted from TM images can well reflect the change of water level in the Poyang Lake,which provided a base for the application of remote sensing technique on forecasting the distribution of snails at bottomland.Part 3:The impact of water level change on snail situation with a small scaleWater is an essential carrier in the spread chain of schistosomiasis,which is also inseparable for the breeding and propagation of snails.The change of water level has an important influence on the distribution of snails.So it is necessary to study the influence on snails situation with the change of water level.We firstly analyzed the influence on the snails situation with the change of water level in small scale.We collected data about water level from 1997 to 2007,to analyse the impact on the distribution of snails in Zhuxi pilot and Xingzi County with the change of water level.The result of statistical analysis showed that there was a negative correlation between the percent of frames with living snails in Zhuxi pilot and average water level of last August(r=-0.748,p=0.013＜0.05).Besides,there is also a negative correlation between the percent of frames with living snails in Zhuxi pilot and average water level during wet period/the highest water level of last year(r=-0.652, p=0.041＜0.05/r=-0.771,p=0.009＜0.01).Thus,we can speculate that the higher water level is in wet period and the longer the flooding period lasts,the higher the mortality rate of snails is and the lower the percent of frames with living snails is.In addition,there is a negative correlation between areas of snails in marshland and lake regions of Xingzi county and the average water level of April(r=-0.761, p=0.011＜0.05),which suggests that if bottomland is submerged in advance or water level rises during spring tide period,the areas of snails in marshland and lake regions may reduce.Part 4:The impact of water level change on the areas of snails in large scalesIn order to further verify the results of part 2,we chose the average monthly water level of Xingzi Hydrometric Station to represent the average water level of the Poyang Lake,and did correlation analysis between the average monthly water level and the snails areas in marshland and lake regions in Jiangxi province.The results showed that there is a negative correlation between areas of snail habitats in marshland and lake regions and the average water level of April(r=-0.658, p=0.039＜0.05),which further suggested that the later the bottomland submerged and the lower the average water level of April was,the larger the areas of snails extended.In the second part,we analyzed the relationship between water areas extracted from TM images and the actual water level data.The results of the third and fourth part suggested that the average water level of last August and April this year influenced the distribution of snails and areas of snail habitats.Thus in practical application,we can collect images of April and August to forecast the distribution and diffusion of snails.更多还原